I Worked as a Security Guard in a Unfinished Building, and Time Went Back

I am a night shift security guard, guarding an empty building that has been in disrepair for 12 years. Until one o'clock in the morning, I found that the time on the 7th floor was running backwards. The phone runs backwards, the wounds heal, the traces disappear, and even myself is being erased bit by bit. The stairs going downstairs turned into a wall. The footsteps upstairs did not belong to humans. My shadow has its own consciousness. I am not the first intruder in this time-retrograde cage. It tells me: You are the 7th. 11 More to go. Floor, that's it.